Asymmetrische Katalysen, 25 [1]. C5H5Mn(CO)2-Komplexe von optisch aktiven Chelatphosphanen als einzähnige Liganden in der enantioselektiven Katalyse / Asymmetric Catalyses, 25 [1]. C5H5Mn(CO)2 Complexes of Optically Active Chelate Phosphanes as Monodentate Ligands in Enantioselective Catalysis

1985 ◽  
Vol 40 (10) ◽  
pp. 1243-1249 ◽  
Author(s):  
Henri Brunner ◽  
Alfons Knott

The chelate phosphanes Diphos, Diop, and Norphos were reacted with C5H5Mn(CO)2THF and CH3C5H4Mn(CO)2THF to give mononuclear complexes, containing the phosphanes as unidentate or as bidentate ligands, and dinuclear complexes, containing bridging phosphane ligands. In C5H5Mn(CO)2Diop one of the two P(C6H5)2 groups of Diop is coordinated to the C5H5Mn(CO)2 fragment; the uncoordinated P(C6H5)2 group makes it a monodentate ligand. C5H5Mn(CO)2Diop together with [Rh(cod)Cl]2 was used as an in situ catalyst in the enantioselective hydrogenation of (Z)-a-[N -acetam ino]cinnamic acid (78.4% ee) and in the enantioselective hydrosilylation of acetophenone with diphenylsilane (6.7% ee).

1983 ◽  
Vol 38 (11) ◽  
pp. 1332-1338 ◽  
Author(s):  
Henri Brunner ◽  
A. F. M. Mokhlesur Rahman

Abstract The chelate ligands 1-3 with lateral asymmetric centers at the nitrogen atoms were prepared and characterized. In the Rh complexes 4 and 5 the asymmetric centers directly interact with those coordination positions where during enantioselective catalysis pro-chiral substrates are converted into optically active products. The compounds 4 and 5, as well as the in situ catalysts [Rh(COD)Cl]2/2 were used in the asymmetric hydrogenation of α-N[acetamino]cinnamic acid and in the asymmetric hydrosilylation of acetophenone with diphenylsilane. The low optical inductions obtained result from the catalyst loosing its chiral information during catalysis due to racemization or fragmentation.


2017 ◽  
Vol 73 (11) ◽  
pp. 1739-1742 ◽  
Author(s):  
Atsuya Koizumi ◽  
Takuya Hasegawa ◽  
Atsushi Itadani ◽  
Kenji Toda ◽  
Taoyun Zhu ◽  
...  

In the title complex, diaqua(1H-imidazole-κN3)(nitrato-κ2O,O′)bis(4-oxopent-2-en-2-olato-κ2O,O′)lanthanum(III), [La(C5H7O2)2(NO3)(C3H4N2)(H2O)2], the La atom is coordinated by eight O atoms of two acetylacetonate (acac) anions acting as bidentate ligands, two water molecule as monodentate ligands, one nitrate anions as a bidentate ligand and one N atom of an imidazolate (ImH) molecule as a monodentate ligand. Thus, the coordination number of the La atom is nine in a monocapped square antiprismatic polyhedron. There are three types of intermolecular hydrogen bonds between ligands, the first involving nitrate–water O...H—O interactions running along the [001] direction, the second involving acac–water O...H—O interactions along the [010] direction and the third involving an Im–nitrate N—H...O interaction along the [100] direction (five interactions of this type). Thus, an overall one-dimensional network structure is generated. The molecular plane of an ImH molecule is almost parallel to that of a nitrate ligand, making an angle of only 6.04 (12)°. Interestingly, the ImH plane is nearly perpendicular to the planes of two neighbouring acac ligands.


1983 ◽  
Vol 61 (6) ◽  
pp. 1347-1351 ◽  
Author(s):  
Michael D. Fryzuk

The synthesis of three coordinatively unsaturated clusters of the formula [{R2PCH2CH2PR2}RhH]x (R = OMe and OEt: x = 4; R = O-i-pr: x = 2) is described starting from the appropriate 2-methylallylrhodium(1) derivatives and H2. The reaction of PMe3 with these clusters results in the formation of mononuclear complexes of the formula HRh(PMe3)2(R2PCH2CH2PR2). Olefins such as 1-hexene do not appear to react with the clusters although a slow isomerization to internal hexenes takes place. The tetranuclear clusters do not form a detectable adduct with H2 up to 4 atm, although exchange with D2 is observed. However, the dinuclear cluster adds one equivalent of H2 per dimer to generate, in situ. [{(i-prO)2PCH2CH2P(O-i-pr)2}2Rh2H4]. These clusters are catalytically active in the hydrogenation of 1-hexene with isomerization to internal hexenes being a competitive process. Although the evidence suggests that the dinuclear derivative does not fragment during the catalytic cycle, the catalytic activity of the tetranuclear clusters may be due to a smaller cluster present in low concentration, generated by fragmentation.


1998 ◽  
Vol 53 (1) ◽  
pp. 126-128 ◽  
Author(s):  
Henri Brunner ◽  
Bernd Haßler

New optically active 3,5-dinitrosalicyloxazolines, derived from 3,5-dinitrosalicylonitrile and the chiral aminodiols (1S,2S)-(+)-2-amino-1-phenyl- 1,3-propanediol, (2S)-(-)-2-amino-1,1,4,4-tetraphenyl- 1,4-butanediol and (2S)-(-)-2-aminol, 1-diphenyl-1,3-butanediol, were prepared and used as in situ catalysts for enantioselective cyclopropanation reactions.


2021 ◽  
Author(s):  
Laksmikanta Adak ◽  
Masayoshi Jin ◽  
Shota Saito ◽  
Tatsuya Kawabata ◽  
Takuma Itoh ◽  
...  

The first enantioselective carbometalation reaction of azabicycloalkenes has been achieved by iron catalysis to in situ form optically active organozinc intermediates, which are amenable to further synthetic elaborations.


2001 ◽  
Vol 12 (15) ◽  
pp. 2213-2222 ◽  
Author(s):  
Nikolai Graf v. Keyserlingk ◽  
Jürgen Martens

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